This invention relates to a fiber optic switch for connecting computer terminals to host computers. Many companies utilize several computer systems to accomplish various tasks. It is sometimes imperative that data from one system be maintained as confidential or proprietary while information from other systems is routinely distributed to the public at large. In such cases it is common to provide separate terminals for each system which are physically and electrically isolated from the other systems. This invention provides considerable cost savings by allowing terminals to address several host computer systems without compromising the integrity of the data contained in the host computers. The use of optical fibers eliminates unintentional communication via electromagnetic radiation emanating from communication cables and common grounds. The present invention provides exclusive two way communication between the terminal and the selected host computer. A temporary power down circuit assures that data stored in volatile RAM (Random Access Memory) in the terminal is erased as the terminal is switched from host system to host system. Fiber optic switches developed in the past have been limited in data transmission rates because of signal losses at the interface between optical fibers in the switch. This invention overcomes those limitations by means of a fluid trapped in a cavity between opposing ends of the optical fibers. The fluid, in intimate contact with the ends of the fibers, has the same optical properties as the central core of the fibers themselves and is thus fully transparent to the light emerging from one fiber and entering the other. This invention also eliminates the need to optically polish the ends of the fibers and thereby saves time and expense during installation. This invention represents the most effective means of establishing a nearly lossless switchable optical connection.